On Mon, Jan 24, 2011 at 11:49 AM, Peter Hickman
<[email protected]> wrote:
> I have a callback (before_save) that I want to trigger only when
> certain fields within a record have changed. For example given a user
> record with 'username', 'password' and 'date_of_birth' I would like
> the callback to do something only when the 'username' or 'password'
> changes or when the 'date_of_birth' changes from nil to something
> real. For example, how would I write...
>
> before_save :audit_changes
>
> def audit_changes
> if old.username != new.username
> audit("The username has changed from #{old.username} to #{new.username})
> end
>
> if old.password != new.password
> audit("The user has changed their password")
> end
>
> if old.date_of_birth == nil and new.date_of_birth != nil
> audit("The user has finally set their date of birth")
> end
> end
>
> Now this is just a little example of what I want to do, don't get hung
> up on the example, but how can I write this?
Active Record has API for that:
http://api.rubyonrails.org/classes/ActiveModel/Dirty.html
so you basically could test whether username_changed?, for example.
The examples in AM::Dirty include the module by hand, but you don't
need to do that in AR models.
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